<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport"
        content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>trim方法去除两侧空格</title>
</head>
<body>
  <input type="text">
  <button>点击</button>
  <div></div>
  <script>
    // trim 方法去除字符串两侧空格     trim() 方法返回一个从两头去掉空白字符的新字符串，并不影响原字符串本身。
    var str = '   an  dy   '
    console.log(str)
    var str1 = str.trim()
    console.log(str1)
    var input = document.querySelector('input')
    var btn = document.querySelector('button')
    var div = document.querySelector('div')
    btn.onclick = function () {
      var str = input.value.trim()
      if (str === '') {
        alert('请输入内容')
      } else {
        // console.log(str)
        // console.log(str.length)
        div.innerHTML = str
      }
    }
  </script>
</body>
</html>